move: log parsers

logparser/v3/log.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org 4
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

logparser/v3/log_err_missing.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

logparser/v3/log_err_negative.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org -100
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

logparser/v3/log_err_str.txt

@@ -0,0 +1,6 @@
+learngoprogramming.com 10
+learngoprogramming.com 10
+golang.org FOUR
+golang.org 6
+blog.golang.org 20
+blog.golang.org 10

logparser/v3/main.go

@@ -0,0 +1,53 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"sort"
+	"strings"
+)
+
+func main() {
+	p := newParser()
+
+	// Scan the standard-in line by line
+	in := bufio.NewScanner(os.Stdin)
+	for in.Scan() {
+		p.lines++
+
+		parsed, err := parse(p, in.Text())
+		if err != nil {
+			fmt.Println(err)
+			return
+		}
+
+		p = update(p, parsed)
+	}
+
+	// Print the visits per domain
+	sort.Strings(p.domains)
+
+	fmt.Printf("%-30s %10s\n", "DOMAIN", "VISITS")
+	fmt.Println(strings.Repeat("-", 45))
+
+	for _, domain := range p.domains {
+		parsed := p.sum[domain]
+		fmt.Printf("%-30s %10d\n", domain, parsed.visits)
+	}
+
+	// Print the total visits for all domains
+	fmt.Printf("\n%-30s %10d\n", "TOTAL", p.total)
+
+	// Let's handle the error
+	if err := in.Err(); err != nil {
+		fmt.Println("> Err:", err)
+	}
+}

logparser/v3/parser.go

@@ -0,0 +1,74 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+// result stores the parsed result for a domain
+type result struct {
+	domain string
+	visits int
+	// add more metrics if needed
+}
+
+// parser keep tracks of the parsing
+type parser struct {
+	sum     map[string]result // metrics per domain
+	domains []string          // unique domain names
+	total   int               // total visits for all domains
+	lines   int               // number of parsed lines (for the error messages)
+}
+
+// newParser constructs, initializes and returns a new parser
+func newParser() parser {
+	return parser{sum: make(map[string]result)}
+}
+
+// parse parses a log line and returns the parsed result with an error
+func parse(p parser, line string) (parsed result, err error) {
+	fields := strings.Fields(line)
+	if len(fields) != 2 {
+		err = fmt.Errorf("wrong input: %v (line #%d)", fields, p.lines)
+		return
+	}
+
+	parsed.domain = fields[0]
+
+	parsed.visits, err = strconv.Atoi(fields[1])
+	if parsed.visits < 0 || err != nil {
+		err = fmt.Errorf("wrong input: %q (line #%d)", fields[1], p.lines)
+		return
+	}
+
+	return
+}
+
+// update updates the parser for the given parsing result
+func update(p parser, parsed result) parser {
+	domain, visits := parsed.domain, parsed.visits
+
+	// Collect the unique domains
+	if _, ok := p.sum[domain]; !ok {
+		p.domains = append(p.domains, domain)
+	}
+
+	// Keep track of total and per domain visits
+	p.total += visits
+
+	// create and assign a new copy of `visit`
+	p.sum[domain] = result{
+		domain: domain,
+		visits: visits + p.sum[domain].visits,
+	}
+
+	return p
+}